1. Field of the Invention
This invention relates to novel acidic heteropolysaccharides and also to a process for preparing such acidic heteropolysaccharides by plant-tissue culture method.
2. Description of the Background
Polysaccharides induced from plants are widely utilized as a viscosity increasing agent, gelatinization agent, foam stabilizer, suspension or emulsion stabilizer, capsule forming agent, adhesives, bioactive agent, and the like.
Conventionally, these polysaccharides are commonly produced from seeds, fruits, stems, trunks, leaves, roots, tubers, or tuberous roots of naturally grown or artificially cultivated plants by tapping, extraction, or the like methods.
Production from the natural sources, however, is liable to be influenced by climatic conditions which tend to cause fluctuation in the production amount and price. Because of this, various trials have been undertaken in recent years to produce these polysaccharides from plants of natural origin by culturing calluses or organa of such plants artificially by means of plant-tissue culture method, thus eliminating the adverse influence of climatic conditions.
There are very few reports concerning the production of polysaccharides of plant origin by plant-tissue culture method application. It is known, however, in relation to research about cell wall development mechanism that small amounts of polysaccharides are secreted in a liquid culture broth wherein a callus is cultured. Reports indicate, for instance, that Vinca rosea L. produces 0.22 gm of polysaccharides per liter of culture broth in 10 days, Glycine max Merril produces 0.49 gm of polysaccharides per liter of culture broth in 8 days, and Phaseolus vulgaris L. produces 1.6 gm of polysaccharides per liter of culture broth in 21 days.
The conventionally utilized plant-tissue culture method, however, has a drawback in its extremely low rate of production. A strong desire has thus existed for the development of a plant-tissue culture method capable of a higher productivity.
In this situation, the present inventors have conducted extensive studies and found that a large amount of polysaccharides was produced by using plants belonging to the genus Polianthes L. as a plant source, and culturing the callus induced therefrom in a culture medium containing one or more plant hormones. The inventors further found that polysaccharides thus produced contained novel acidic heteropolysaccharides which were different from any polysaccharides which were conventionally known. Such findings have led to the completion of this invention.